changelogs/s2s: add minimum_valid_until_ts clarification

Signed-off-by: famfo <famfo@famfo.xyz>

changelogs/server_server/newsfragments/2191.clarification

@@ -0,0 +1 @@
+Clarify what the minimum_valid_until_ts field means when it is set in key queries.

data/api/server-server/keys_query.yaml

@@ -34,8 +34,8 @@ paths:
         - in: query
           name: minimum_valid_until_ts
           description: |-
-            A millisecond POSIX timestamp in milliseconds indicating when the returned
-            certificates will need to be valid until to be useful to the requesting server.
+            A millisecond POSIX timestamp indicating until when the returned
+            keys MUST at least be valid.
 
             If not supplied, the current time as determined by the notary server is used.
           required: false
@@ -98,9 +98,8 @@ paths:
                           type: integer
                           format: int64
                           description: |-
-                            A millisecond POSIX timestamp in milliseconds indicating when
-                            the returned certificates will need to be valid until to be
-                            useful to the requesting server.
+                            A millisecond POSIX timestamp indicating until when
+                            the returned keys MUST at least be valid.
 
                             If not supplied, the current time as determined by the notary
                             server is used.